On luci side:
Disable dhcpv6 by editing the lan interface>dhcp tab>disable
On CLI side:

cd /etc/config
vi firewall
# Uncomment this line to disable ipv6 rules
        option disable_ipv6     1 

cd /etc/
vi sysctl.conf
net.ipv6.conf.all.disable_ipv6 = 1 

(Last edited by chronoman on 28 Dec 2015, 02:00)

Thanks for that, I wanted to automate it, so here's how it can also be done from the console:

uci delete dhcp.lan.ra
uci delete dhcp.lan.dhcpv6
uci set firewall.@defaults[0].disable_ipv6=1
sed -i '/net.ipv6.conf.all.forwarding=1/a net.ipv6.conf.all.disable_ipv6=1' /etc/sysctl.conf
uci commit dhcp
uci commit firewall

Thanks for the info....by the way what are the advantages to disable ipv6?

I found a new way which completely removes ipv6 support. Before you follow this backup the ipv6 modules.
1-

lsmod | grep ipv6

check modules
2-

cd /lib/modules/*/

Delete the ipv6 modules
such as ipv6.ko, etc. . .
3-

reboot

(Last edited by chronoman on 25 Dec 2015, 02:33)

Do any of these options also modify the GUI accordingly?

hi, I applied all of the above solutions after disabling ipv6 in the GUI, that seems to work nicely.

There are _no_ advantages. If one wants to live in the last century, and ignore that IPv6 is the future of the internet.  All growth and expansion of the internet is on IPv6, since there are NO more IPv4 addresses left (in North America).